This invention relates generally to composite thermoplastic articles and more particularly to a method of electromagnetically welding thermoplastic articles together.
Modern automotive door trim panels comprise a structural thermoplastic substrate that is covered by a soft decorative cover or cloth, leather or thermoplastic material for aesthetic purposes. Such door trim panels, particularly those for upscale models, often include a carpet face panel on the lower portion of the door trim panel where the door trim panel is particularly susceptible to wear and tear. See for instance U.S. Pat. No. 5,073,318 granted to Milo L. Rohriach and William J. Hall on Dec. 17, 1991 for a door trim panel that includes a carpet face panel that is attached to the lower portion of a facing layer of a trim panel by an adhesive.
It is also known that a carpet face panel can be electromagnetically welded directly to a thermoplastic substrate of a door trim panel. In this known method magnetic particles of metal, iron, or other magnetic material that can be heated dielectrically or by induction are mixed into an adhesive that is applied to the bond surface of the thermoplastic substrate. A carpet face panel, which has been molded to shape is then pressed against the adhesively coated bond surface of the thermoplastic substrate. A high frequency current in the radio frequency range is then applied to an electromagnet beneath the bond surface of the substrate. This heats the magnetic particles which in turn heat and melt the abutting plastic surfaces of the carpet face panel and the to weld these surfaces together. See also U.S. Pat. No. 3,574,031 granted to W. C. Heller, Jr. and A. F. Leatherman Apr. 6, 1971 for a method of heat welding thermoplastic bodies using a stratum of susceptor material and U.S. Pat. No. 3,941,641 granted to William C. Heller, Jr. and Alfred F. Leatherman Mar. 2, 1976 for a bonding method and apparatus.